There are certain advantages in beamrider guidance systems over terminal homing and command guidance systems for directing a missile toward a target. For example, because it is located on the rear of the missile and faces rear, the beamrider receiver is less vulnerable to countermeasures than the terminal homing receiver and the beacon tracker of the command guidance systems.
Briefly, performing beamrider guidance involves establishing a sight line to the selected target by optical or other suitable means and aligning the center line of the beam projector with the sight line. The beam that is emitted from the beam projector along the sight line is spatially encoded so that one part of the beam has some characteristic that renders it distinguishable from the other parts of the beam. This is usually accomplished by having a separate modulator for each part of the beam that imparts a distinguishing characteristic to each part. Into this beam, then, is the missile launched. The beamrider receiver on the missile senses the missile position relative to the center line of the modulated beam and develops command signals that constrain the missile to fly down the center line to the target. However, the optical or infrared beamrider guidance system is limited in usability because the rocket exhaust, dust and debris generated during launching tends to obscure the missile during the initial stage of the flight while weather effects may impair guidance performance during later stages.